Public bathrooms house thousands of kinds of bacteria

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Rob Dunn is a science writer and biologist in the Department of Biology at North Carolina State University. His first book, Every Living Thing, told the stories of the sometimes obsessive, occasionally mad, and always determined, biologists who have sought to discover the limits of the living world. His new book, The Wild Life of Our Bodies, explores how changes in our interactions with other species, be they the bacteria on our skin, forehead mites or tigers, have affected our health and well being. Rob lives in Raleigh, North Carolina with his wife, two children, and lots of microbes. Follow on Twitter @RobRDunn.

…especially on toilets which, by the way, saved humanity, changed our ecology, and made the modern city possible.

If you are the sort of person who does not like to use public restrooms, I will warn you right now, this article is going to cause you some concern. It may lead you to hold it until you get home. It may even lead you to abandon bathrooms altogether for a bear’s life of pooping in the woods. The bears, after all, never have to worry about whether or not to put toilet paper around the rim of the seat. Then again, bears also don’t live in cities with million of other pooping bears.

I am getting ahead of myself a little. Before we get to what is living in public restrooms, we need to better understand the toilet, the restroom’s glamorous raison d’être. It is remarkably hard to identify the person who invented the first flushing toilet. Brighter minds have tried and failed. Praise is sometimes leveled on Sir Thomas Crapper. Crapper was a toilet visionary—no question. But crapper did not invent the flushing toilet, he just elaborated upon existing designs (Crap is not named for him, though that would be a better story.) [1]. Truth is, toilets are one of those inventions that followed need and so arose independently all around the world when the alternatives went from terrible to unbearable.

In urban Europe from the 1500s until the mid-1800s most homes lacked indoor plumbing. Folks were content to use chamber pots emptied out of windows with a heave. When throwing one’s feces out a window it was polite to yell some version of “look out below.” When accidentally walking under such falling feces, one assumes the standard thing to yell back was “oh crap.” With time, feces accumulated beneath windows to a depth that required shoveling. This and a general preponderance of waste eventually led to the use of indoor, flushing, toilets, but not until the 1850s. Until then, European cities reeked of filth and decay. The good ole days of London and other major cities were, at least for people, not so good.

The problem with waste is not its smell, which is vulgar and unpleasant but ultimately without consequence. The problem is the life that thrives in what we leave behind, species that would love nothing more than to pass from one person to another via feces forever, the way that an ugly family heirloom is passed among generations. These creatures include deadly microbes such as those that cause cholera, dysentery, and typhoid fever and then also crazy hook-faced animals like hookworms, pinworms, tapeworms and roundworms (whose presence may actually have offered some benefit). When waste was everywhere in cities, these species thrived. They bet on the odds and the odds were that if you waited around long enough in feces you would make contact with another human, whether directly or by hitching a ride on, say, an insect species. For centuries, the streets were alive with the sounds of flies, many of them ferrying disease.

Eventually the flushing toilet began to become common and then, as the causes of cholera and other diseases were discovered, the norm. [2] Slowly, the urban experience changed. Toilets saved human lives by making it harder for the species in our waste to move person to person. Just how many lives were saved is impossible to know, though I would wager tens of millions. Sinks saved lives by making it easy to wash our hands, toilets saved lives by causing there to be fewer things to wash from our hands. In this sense, bathrooms with their porcelain centerpieces are the healthiest places in our modern society, the rooms for which we should be most grateful. Bless you bathrooms not for what you are, but for what you have saved us from.

I wanted to establish the value of the toilet, public or otherwise, before discussing the results of the new study published today in PLoS ONE, results that are going to make you feel as though toilets and bathrooms are, well, not good. In this study, Gilberto Flores, his mentor Noah Fierer and other colleagues at the University of Colorado, Boulder studied twelve public bathrooms at the University of Colorado. The sampling was simple. Two postdocs on the team, Scott Bates and Christian Lauber, appear to have drawn the short straws and were sent to swab a variety of locations in each of the bathrooms. They swabbed stall handles, soap dispensers, toilet seats, toilet flush handles, the floor and more. The samples of these bathrooms were then taken back to the lab where the team used genetic techniques, a kind of molecular microscope, to reveal which species were present but invisible in the bathrooms. [3] This study was the first of its kind in the history of humanity, the first clean look at our dirt.

Certainly, this is not the first study of the life in bathrooms. Sociological studies consider the foot movements of senators in public restrooms. Psychological studies consider the effect of public bathrooms on people who have trouble peeing (it makes it worse). Sexual studies consider what can be learned from the graffiti in public bathrooms (that most people can’t spell dirty words). Then there are the studies of germs in bathrooms. Beginning in the 1960s, an entire field of science aimed to understand the story of bathroom bacteria [4]. These studies revealed that when you flush the toilet with the lid up that bacteria can go up to six feet through the air (including onto your toothbrush), that students very rarely wash their hands, that bacteria are present all over the bathroom though differ between wet versus dry places, and that, so long as the lid is closed, flushing the toilet is actually a pretty good way to get rid of bacteria such that toilet bowls don’t have that many bacteria. If you know some factoid about bacteria in bathrooms, you know it from these studies. BUT all of these studies miss something, namely most of the species.

What no one until Flores, Fierer and crew had done was to study those species of bacteria that do not/will not/cannot grow in petri dishes. Everything you (and scientists) know about the bacteria in bathrooms is based just on those species we know enough about to “feed” in the lab. So what about the other species? They tell, it turns out, other stories.

Flores and colleagues discovered thousands of species in the twelve bathrooms they surveyed, more kinds of bacteria than there are kinds of birds in North America.

Those thousands of bacteria species seemed to be composed of three groups corresponding to just how they arrived in the bathroom—gut species, skin species and shoe species. Species associated with human guts or feces were common on toilet flush handles and toilet seats, where they were either sprayed when the toilets flushed or transferred on hands. Species associated with human skin were common on door handles and other surfaces frequently touched by hands, though not necessarily hands with any feces on them. Finally, the floor community was sparse but diverse, with many rare species found here and there among the tiles, as though our feet were bringing bacteria in from all over the world, each and every place we, or at least the visitors to these particular bathrooms, had been.

The more Flores and colleagues looked to the bacteria for evidence of how we use bathrooms, the more they saw. Bacteria species like those found on the floor were found on some toilet flush handles. This finding is, Flores suspects, evidence of the ways in which some people flush, with their feet. Also, bacteria species typically found in vaginas were common on women’s but not on men’s toilets, one more microbial measure of who has visited. None of the areas tested in bathrooms had bacteria similar to those found in tap water (another potential source). Instead, most of the species appear to have come in the old fashioned way, on us. The bacteria present in any particular bathroom appear to be a measure of the process of colonization, wherein the lifeless tiles, plastic and ceramic are reinvigorated with species. One could go to Krakatau to study the process by which life colonizes non-life (volcanic rock in Krakatau’s case). Flores and company go to the john.

Flores and colleagues have, in the end, discovered our bathrooms to be yet another everyday wilderness, still largely unknown. Some of the species they found are new arrivals, having traveled to the bathroom for the first time on someone’s hand, belly or unmentionable part. Others have been traveling with us for generations, moving bathroom to bathroom, as they once moved chamber pot to pot. These include pathogen species we need to scrub away with soap and water (though not antimicrobial wipes). But just as significant as what Flores and colleagues found is what they did not. They did not find cholera or typhoid (or for that matter any worms). They did not see them because of the toilet. The toilet continues to be what separates us from the most terrible of the beasts, the ones that Flores didn’t discover (but that he likely would have found in countries where toilets are rare), species that since the 1850s we have largely flushed away. And so hover over the seat if Flores’s study worries you. But as you do so, be grateful, for the invention below your intentions, a breakthrough that as much as antibiotics or heart surgery is likely to save your life, whether you know it or not, one uncelebrated flush at a time.

[1]-Queen Elisabeth’s dirty poet, John Harrington, who was, it is said, more dirty than poet may have actually invented one of the first flush toilets in the late 1500s. Queen Elisabeth appears to have tried the toilet out and liked it so much she ordered one herself, giving rise to the first royal flush. The very first toilets, however, are much older with toilets “flushed” with water having been recorded as early as 2000 BC in Pakistan.

[2]-Though even today it remains common only some places. By some estimates 4 out of 10 people in the world still lack hygienic waste disposal, whether it be via outhouse (how my sister lives), dry toilet, or flush toilet.

[3]-16S rRNA barcoded pyrosequencing for any hipster readers who need to know.

[4]-For example the classic paper by Elizabeth Scott and colleagues from 1982, “An investigation of microbial contamination in the home (J. Hyg. 89: 279-293” in which Scott and clan consider the microbes (that grow on petri dishes) from each of 200 homes.

About the Author:Rob Dunn is a science writer and biologist in the Department of Biology at North Carolina State University. His first book, Every Living Thing, told the stories of the sometimes obsessive, occasionally mad, and always determined, biologists who have sought to discover the limits of the living world. His new book, The Wild Life of Our Bodies, explores how changes in our interactions with other species, be they the bacteria on our skin, forehead mites or tigers, have affected our health and well being. Rob lives in Raleigh, North Carolina with his wife, two children, and lots of microbes. Follow on Twitter @RobRDunn.